Stuffing boxes are used in the oilfield to form a seal between the wellhead and a well tubular passing through the wellhead, in order to prevent leakage of wellbore fluids between the wellhead and the piping. Stuffing boxes may be used in a variety of applications, for example production with pump-jacks, and inserting or removing coiled tubing. Stuffing boxes may incorporate a tubular shaft mounted for rotation in the housing for forming a stationary seal with the piping in order to rotate with the piping. The tubular shaft in turn dynamically seals with the stuffing box housing. Designs of this type of stuffing box can be seen in the following patents: U.S. Pat. No. 7,044,217 and CA 2,350,047. In other designs, the stuffing box may instead form a dynamic seal directly against the piping without incorporating a rotating tubular shaft. Stuffing boxes may be used for rotating or reciprocating pumps.
Drive heads are used in tandem with stuffing boxes. In some cases the drive head sits above the stuffing box. In other cases the stuffing box is incorporated into the drive head or sits above the drive head, for example in FIG. 3 of U.S. Pat. No. 7,044,217.
Leakage of crude oil from a stuffing box is common in some applications, due to a variety of reasons including abrasive particles present in crude oil and poor alignment between the wellhead and stuffing box. Leakage costs oil companies money in service time, down-time and environmental clean-up. Leakage is especially a problem in heavy crude oil wells in which oil may be produced from semi-consolidated sand formations where loose sand is readily transported to the stuffing box by the viscosity of the crude oil. Costs associated with stuffing box failures are some of the highest maintenance costs on many wells.